diff --git a/expat/lib/xmltok.c b/expat/lib/xmltok.c
--- a/expat/lib/xmltok.c
+++ b/expat/lib/xmltok.c
@@ -1148,6 +1148,10 @@ static const char KW_yes[] = {ASCII_y, A
 
 static const char KW_no[] = {ASCII_n, ASCII_o, '\0'};
 
+/* BEGIN MOZILLA CHANGE (Bug 62157 - Document content is rendered even though version value is not "1.0") */
+static const char KW_XML_1_0[] = {ASCII_1, ASCII_PERIOD, ASCII_0, '\0'};
+/* END MOZILLA CHANGE */
+
 static int
 doParseXmlDecl(const ENCODING *(*encodingFinder)(const ENCODING *, const char *,
                                                  const char *),
@@ -1175,6 +1179,13 @@ doParseXmlDecl(const ENCODING *(*encodin
       *versionPtr = val;
     if (versionEndPtr)
       *versionEndPtr = ptr;
+/* BEGIN MOZILLA CHANGE (Bug 62157 - Document content is rendered even though version value is not "1.0") */
+     /* Anything else but a version="1.0" is invalid for us, until we support later versions. */
+     if (!XmlNameMatchesAscii(enc, val, ptr - enc->minBytesPerChar, KW_XML_1_0)) {
+       *badPtr = val;
+       return 0;
+     }
+/* END MOZILLA CHANGE */
     if (! parsePseudoAttribute(enc, ptr, end, &name, &nameEnd, &val, &ptr)) {
       *badPtr = ptr;
       return 0;